Hospital workers constitute the third largest employee group in the United States, about three million individuals. The majority of these workers are of reproductive age and over 75 percent are female. It is well known that these individuals have exposure to a wide variety of agents known to affect reproduction. For example, infectious diseases are an obvious hazard of hospital work and several infectious agents are known reproductive hazards. Exposure to anesthetic gasses and ionizing radiation have been found to increase the risk of spontaneous abortion. To date, a systematic study of the reproductive experiences of this group has not been attempted. Therefore, the objective of this study is to determine whether hospital workers are at increased risk for adverse reproductive outcomes. The proposed study is a case-control analysis of birth outcomes within a large cohort of hospital workers, designed to identify associations between exposures within the hospital industry and selected adverse reproductive outcomes. The primary outcome to be examined is low birthweight infants (less than 2,500 g). Congenital anomalies, among offspring of hospital workers will also be examined but sample sizes may limit the ability to detect all but a marked increase in risk. The ability to conduct this study rests in our long standing relationship with District 1199, National Union of Hospital and Health Care Workers, representing over 130,000 members nationwide. The union will provide full access to its health and membership records. Data from the unions comprehensive benefit plan and birth certificates will be used to identify cases and controls. A structured telephone interview conducted with both cases and controls will provide data on occupational histories, job location and duties and specific exposures. We will also gather information on socioeconomic factors, reproductive history and other potentially confounding variables. Data analysis will explore and measure the strength of associations between exposures and the selected reproductive outcome. The influence of potential confounding variables will be assessed. We believe that this study provides an unique opportunity to assess the relationship between hospital exposures and adverse reproductive outcomes, e.g. low birthweight and congenital malformations in a large group of working women and men.